Crayfish, of which our own Northern Crayfish (Orconectes virilis) is one of about 500 species worldwide, are crustaceans related to copepods, barnacles, crabs, shrimps, lobsters, etc. The Northern Crayfish grows to a length of about 10-12 cm, not including the 2 pairs of long antennae or the large chelipeds, the large claw or pincer bearing legs that extend forward.
The chelipeds often have a bluish tint, particularly in the males which have larger chelipeds and larger pincers than females. The head and thorax are covered by a shell-like carapace, usually brownish to rusty red in colour. There are four pairs of jointed walking legs called pereopods also attached to the thorax. (The chelipeds are actually modified pereopods.) The jointed abdomen, which can be folded under the thorax, has 5 pairs of small limbs called pleopods, or swimmerets.
The first two pleopods of males are modified to aid in sperm transfer. In female crayfish the first two pleopods look the same as all the rest. In crayfish the pleopods beat to maintain a current of water over the feather-like gills which are located along the sides of the thorax beneath the carapace. At the end of the abdomen is the telson, which together with the paddle-shaped uropods forms a flipper-like tail. A crayfish normally walks forward on its pereopods, but when frightened it flips its tail rapidly and repeatedly under its thorax and scoots away backwards.
Scientific Classification:-
| Kingdom |
: |
Animalia |
| Phylum |
: |
Arthropoda |
| Subphylum |
: |
Crustacea |
| Class |
: |
Malacostraca |
| Order |
: |
Decapoda |
| Suborder |
: |
Pleocyemata |
| Infraorder |
: |
Astacidea |
| Superfamily |
: |
Astacoidea |